One of the most important and distinguishing features of wireless communications is the ability of the mobile station to roam between systems. While roaming, a mobile station typically will select a system made available by a cellular provider in the geographic area where the subscriber is roaming based on its custom system selection method, which emphasizes finding a system (any system) for service. The draw back of this prior approach is that the mobile station does not have any knowledge whether the selected system is the most desirable system, in the sense of whether a more preferred system in a given market (geographic location) may exist for providing better service in terms of roaming rate and compatible services. This makes roaming between systems a big concern from the end user's perspective, which in the past has directly impacted the growth of the wireless market.
With the introduction of PCS, at any given geographical location, there could eventually be eight wireless systems providing services. Two of them would of course be cellular A-side and B-side service providers at the 800 MHz range. The other six are new comers (Blocks A, B, C, D, E, and F) operating at the 1.9 GHz spectrum. In addition, there are two other factors that have contributed to further confusing the roaming situation even further:
1) In this growing market place, more and more preferred roaming agreements will be established between different service providers in different geographic markets. Considering the fact that today, there are 306 Metropolitan Service Areas MSAs and 428 Rural Service Areas RSAs (each MSA or RSA having 2 cellular operators), and 543 MTAs (Major Trading Area) and BTAs (Basic Trading Area). Each region or area may have up to 6 PCS operators. Because of this large number of operators in the U.S., the number and level of preferred roaming agreements could soon become overwhelming. With the enactment of the U.S. Telecommunications Act in 1996, more and more alliances and mergers of service providers in the market place are predicted. This creates further confusion to the mobile station as to how it can select a system while roaming having a preferred agreement with its home service provider.
2) With the auction of the PCS spectrum, some service providers now own different segments of the air spectrum in different geographic locations. It is then imperative for mobile stations to be able to access systems provided by the same service provider in different geographic markets to get preferred rates and to preserve the services that the subscriber has with its home base system.
In short, competition in wireless services and service provider's desire to offer seamless roaming will make the wireless market place more dynamic and vibrant, which in turn impacts the mobile station's ability to select a favorable system. It is the purpose of this invention to develop a new method, which relies on the intelligence in the network (particularly the Home Location Register, HLR), to guide the mobile station to a preferred cellular provider in any market into which it roams.